Method and structure for enabling controlled spacer RIE

ABSTRACT

A method and structure to enable reliable dielectric spacer endpoint detection by utilizing a sacrificial spacer fin are provided. The sacrificial spacer fin that is employed has a same pitch as the pitch of each semiconductor fin and the same height as the dielectric spacers on the sidewalls of each semiconductor fin. Exposed portions of the sacrificial spacer fin are removed simultaneously during a dielectric spacer reactive ion etch (RIE). The presence of the sacrificial spacer fin improves the endpoint detection of the spacer RIE and increases the endpoint signal intensity.

BACKGROUND

The present application relates to semiconductor manufacturing, and moreparticularly to a method and structure to enable improved dielectricspacer reactive ion etch (RIE) endpoint detection.

For more than three decades, the continued miniaturization of metaloxide semiconductor field effect transistors (MOSFETs) has driven theworldwide semiconductor industry. Various showstoppers to continuedscaling have been predicated for decades, but a history of innovationhas sustained Moore's Law in spite of many challenges. However, thereare growing signs today that metal oxide semiconductor transistors arebeginning to reach their traditional scaling limits. Since it has becomeincreasingly difficult to improve MOSFETs and therefore complementarymetal oxide semiconductor (CMOS) performance through continued scaling,further methods for improving performance in addition to scaling havebecome critical.

The use of non-planar semiconductor devices such as, for example,semiconductor fin field effect transistors (FinFETs) is the next step inthe evolution of complementary metal oxide semiconductor (CMOS) devices.Semiconductor fin field effect transistors (FETs) can achieve higherdrive currents with increasingly smaller dimensions as compared toconventional planar FETs.

In the fabrication of FinFET devices, a controlled dielectric spacerpull down process is critical to enable source/drain epitaxy growth andprevent the formation of an epitaxial semiconductor nodule. Utilizingcurrent technology, the control of a spacer pull down process ischallenging because there is no reliable endpoint signal to detect.Moreover, the current processes for the removal of a dielectric spacerthat is present on top of an insulator layer as well as on the sidewallsurfaces of a semiconductor fin that extend upwards from the insulatorlayer do not provide enough of an endpoint detection signal change forreliable endpoint detection.

As such, there is a need for providing a method and structure to enabledielectric spacer endpoint detection that overcomes the problemsassociated with prior art processes of removing dielectric spacersduring fabrication of finFET devices.

SUMMARY

A method and structure to enable reliable dielectric spacer endpointdetection by utilizing a sacrificial spacer fin are provided. Thesacrificial spacer fin that is employed has a same pitch as the pitch ofeach semiconductor fin and the same height as the dielectric spacers onthe sidewalls of each semiconductor fin. Exposed portions of thesacrificial spacer fin are removed simultaneously during a dielectricspacer reactive ion etch (RIE). The presence of the sacrificial spacerfin improves the endpoint detection of the spacer RIE and increases theendpoint signal intensity.

In one aspect of the present application, a method of forming asemiconductor structure is provided. In one embodiment of the presentapplication, the method includes providing a plurality of semiconductorfins extending upwards from a surface of a substrate, and a plurality ofsacrificial spacer fins extending upwards from another surface of thesubstrate. Next, a sacrificial gate structure is formed straddling overa portion of each semiconductor fin and each sacrificial spacer fin. Adielectric spacer material is then formed surrounding the sacrificialgate structure, wherein the dielectric spacer material and eachsacrificial spacer fin comprise a same dielectric material. Next, aspacer reactive ion etch is performed to the dielectric spacer materialto provide a dielectric spacer on sidewall surfaces of the sacrificialgate structure, wherein during the spacer reactive ion etch exposedportions of each sacrificial spacer fin are removed.

In another aspect of the present application, a semiconductor structureis provided. In one embodiment of the present application, thesemiconductor structure includes a plurality of semiconductor finsextending upwards from a surface of a substrate, and a plurality ofsacrificial spacer fin portions extending upwards from another surfaceof the substrate. A gate structure straddles over each semiconductor finand each sacrificial spacer fin portion. A gate (i.e., dielectric)spacer surrounds the gate structure. Each sacrificial spacer fin portionis located entirely beneath a portion of the gate structure and aportion of the gate spacer.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A is top-down view of an exemplary semiconductor structureincluding, from bottom to top, a handle substrate, an insulator layerand a semiconductor material layer that can be employed in accordancewith an embodiment of the present application.

FIG. 1B is a cross-sectional view of the first exemplary semiconductorstructure of FIG. 1A along the vertical plane B-B′.

FIG. 2A is a top-down view of the exemplary semiconductor structure ofFIGS. 1A-1B after forming a plurality of semiconductor fins, i.e., afirst set of semiconductor fins and a second set of semiconductor fins,extending upwards from a surface of the insulator layer.

FIG. 2B is a cross-sectional view of the first exemplary semiconductorstructure of FIG. 2A along the vertical plane B-B′.

FIG. 3A is a top-down view of the exemplary semiconductor structure ofFIGS. 2A-2B after forming a protective dielectric liner on exposedsurfaces of each semiconductor fin and on exposed portions of theinsulator layer.

FIG. 3B is a cross-sectional view of the first exemplary semiconductorstructure of FIG. 3A along the vertical plane B-B′.

FIG. 4A is a top-down view of the exemplary semiconductor structure ofFIGS. 3A-3B after forming a sacrificial dielectric material.

FIG. 4B is a cross-sectional view of the first exemplary semiconductorstructure of FIG. 4A along the vertical plane B-B′.

FIG. 5A is a top-down view of the exemplary semiconductor structure ofFIGS. 4A-4B after removing an upper portion of the sacrificialdielectric material and a portion of the protective dielectric liner toexpose a topmost surface of each semiconductor fin.

FIG. 5B is a cross-sectional view of the exemplary semiconductorstructure of FIG. 5A along the vertical plane B-B′.

FIG. 6A is a top-down view of the exemplary semiconductor structure ofFIGS. 5A-5B after forming a block mask structure over the first set ofsemiconductor fins, while leaving the second set of semiconductor finsexposed.

FIG. 6B is a cross-sectional view of the exemplary semiconductorstructure of FIG. 6A along the vertical plane B-B′.

FIG. 7A is a top-down view of the exemplary semiconductor structure ofFIGS. 6A-6B after removing each semiconductor fin of the second set ofsemiconductor fins.

FIG. 7B is a cross-sectional view of the exemplary semiconductorstructure of FIG. 7A along the vertical plane B-B′.

FIG. 8A is a top-down view of the exemplary semiconductor structure ofFIGS. 7A-7B after removing the block mask structure and forming asacrificial spacer material.

FIG. 8B is a cross-sectional view of the exemplary semiconductorstructure of FIG. 8A along the vertical plane B-B′.

FIG. 9A is a top-down view of the exemplary semiconductor structure ofFIGS. 8A-8B after removing an upper portion of the sacrificial spacermaterial to provide sacrificial spacer fins within an area previouslyoccupied by the second set of semiconductor fins.

FIG. 9B is a cross-sectional view of the exemplary semiconductorstructure of FIG. 9A along the vertical plane B-B′.

FIG. 10A is a top-down view of the exemplary semiconductor structure ofFIGS. 9A-9B after removing remaining portions of the sacrificialdielectric material and remaining portions of the protective dielectricliner.

FIG. 10B is a cross-sectional view of the exemplary semiconductorstructure of FIG. 10A along the vertical plane B-B′.

FIG. 11A is a top-down view of the exemplary semiconductor structure ofFIGS. 10A-10B after forming another protective dielectric liner onexposed surfaces of each semiconductor fin of the first set ofsemiconductor fins, on exposed surfaces of each sacrificial spacer finand on exposed portions of the insulator layer.

FIG. 11B is a cross-sectional view of the exemplary semiconductorstructure of FIG. 11A along the vertical plane B-B′.

FIG. 12A is a top-down view of the exemplary semiconductor structure ofFIGS. 10A-10B after forming a sacrificial gate material and aphotoresist material.

FIG. 12B is a cross-sectional view of the exemplary semiconductorstructure of FIG. 12A along the vertical plane B-B′.

FIG. 13A is a top-down view of the exemplary semiconductor of FIGS.12A-12B after forming sacrificial gate structures straddling overdifferent portions of each semiconductor fin of the first set ofsemiconductor fins and each sacrificial spacer fin.

FIG. 13B is a cross-sectional view of the exemplary semiconductorstructure of FIG. 13A along the vertical plane C-C′.

FIG. 14A is a top-down view of the exemplary semiconductor structure ofFIGS. 13A-13B after forming a dielectric spacer material.

FIG. 14B is a cross-sectional view of the exemplary semiconductorstructure of FIG. 14A along the vertical plane C-C′.

FIG. 15A is a top-down view of the exemplary semiconductor structure ofFIGS. 14A-14B after performing a spacer reactive ion (RIE) etch.

FIG. 15B is a cross-sectional view of the exemplary semiconductorstructure of FIG. 15A along the vertical plane C-C′.

FIG. 15C is a cross-sectional view of the exemplary semiconductorstructure of FIG. 15A along the vertical plane D-D′.

FIG. 15D is a cross-sectional view of the exemplary semiconductorstructure of FIG. 15A along the vertical plane E-E′.

FIG. 16A is a top-down view of the exemplary semiconductor structure ofFIGS. 15A-15D after replacing each sacrificial gate structure with afunctional gat structure.

FIG. 16B is a cross-sectional view of the exemplary semiconductorstructure of FIG. 16A along the vertical plane C-C′.

DETAILED DESCRIPTION

The present application will now be described in greater detail byreferring to the following discussion and drawings that accompany thepresent application. It is noted that the drawings of the presentapplication are provided for illustrative purposes only and, as such,the drawings are not drawn to scale. It is also noted that like andcorresponding elements are referred to by like reference numerals.

In the following description, numerous specific details are set forth,such as particular structures, components, materials, dimensions,processing steps and techniques, in order to provide an understanding ofthe various embodiments of the present application. However, it will beappreciated by one of ordinary skill in the art that the variousembodiments of the present application may be practiced without thesespecific details. In other instances, well-known structures orprocessing steps have not been described in detail in order to avoidobscuring the present application.

Referring first to FIGS. 1A-1B, there are illustrated various views ofan exemplary semiconductor structure including, from bottom to top, ahandle substrate 10, an insulator layer 12 and a semiconductor materiallayer 14 that can be employed in accordance with an embodiment of thepresent application. Collectively, the handle substrate 10, theinsulator layer 12 and the semiconductor material layer 14 may bereferred to herein as a semiconductor-on-insulator (SOI) substrate. Thehandle substrate 10 provides mechanical support for the insulator layer12 and the semiconductor material layer 14.

In some embodiments of the present application, the handle substrate 10may comprise a semiconductor material. The term “semiconductor” as usedherein in connection with the semiconductor material of the handlesubstrate 10 (or any other semiconductor material described herein)denotes any material that exhibits semiconductor properties including,for example, Si, Ge, SiGe, SiC, SiGeC, a II/VI compound semiconductor ora III/V compound semiconductor such as, for example, InAs, GaAs, or InP.In one embodiment, the handle substrate 10 may be comprised of silicon.In some embodiments, the handle substrate 10 is a non-semiconductormaterial including, for example, a dielectric material and/or aconductive material. In yet other embodiments, the handle substrate 10can be omitted and a substrate including insulator layer 12 and thesemiconductor material layer 14 can be used in the present application.

The semiconductor material layer 14 may comprise one of thesemiconductor materials mentioned above for the handle substrate 10. Inone embodiment, the semiconductor material layer 14 comprises a samesemiconductor material as the handle substrate 10. In anotherembodiment, the semiconductor material layer 14 comprises a differentsemiconductor material than the handle substrate 10. In one embodiment,the semiconductor material layer 14 comprises silicon.

In some embodiments, the handle substrate 10 and the semiconductormaterial layer 14 may have a same crystal orientation. In otherembodiments, the handle substrate 10 and the semiconductor materiallayer 14 may have different crystal orientations. The crystalorientation of the handle substrate 10 and/or the semiconductor materiallayer 14 may be {100}, {110}, or {111}. Other crystallographicorientations besides those specifically mentioned can also be used inthe present application. The handle substrate 10 may be a singlecrystalline semiconductor material, a polycrystalline material, or anamorphous material. The semiconductor material layer 14 is typicallycomprised of a single crystalline semiconductor material such as, forexample, single crystalline silicon.

The insulator layer 12 of the exemplary semiconductor structure shown inFIGS. 1A-1B may be a crystalline or non-crystalline oxide and/ornitride. In one embodiment, the insulator layer 12 is an oxide such as,for example, silicon dioxide. In another embodiment, the insulator layer12 is a nitride such as, for example, silicon nitride or boron nitride.In yet still another embodiment of the present application, theinsulator layer 12 may be a multilayered structure such as a stack of,in any order, silicon dioxide and boron nitride.

The exemplary semiconductor structure including the handle substrate 10,the insulator layer 12, and the semiconductor material layer 14 may beformed utilizing standard processes known in the art. In one example,the exemplary semiconductor structure shown in FIGS. 1A-1B may be formedby SIMOX (Separation by IMplantation of OXygen). In another example, alayer transfer process including wafer bonding may be used to providethe exemplary semiconductor structure shown in FIGS. 1A-1B.

The thickness of the semiconductor material layer 14 that can be used inthe present application can be from 10 nm to 150 nm. Other thicknessesthat are lesser than, or greater than, the aforementioned range can alsobe employed in the present application as the thickness of thesemiconductor material layer 14. The thickness of the insulator layer 12that may be used in the present application can be from 10 nm to 200 nm.Other thicknesses that are lesser than, or greater than, theaforementioned thickness range for the insulator layer 12 can also beused in the present application. The thickness of the handle substrate10 of the exemplary semiconductor structure shown in FIGS. 1A-1B isinconsequential to the present application.

In some embodiments, the exemplary semiconductor structure shown inFIGS. 1A-1B may a bulk semiconductor substrate. By “bulk” it is meantthat the entirety of the exemplary semiconductor structure shown inFIGS. 1A-1B comprises one or more semiconductor materials as definedabove for handle substrate 10.

Referring now to FIGS. 2A-2B, there are illustrated various views of theexemplary semiconductor structure of FIGS. 1A-1B after forming aplurality of semiconductor fins (14L, 14R) extending upwards from asurface of the insulator layer 12. In this embodiment, insulator layer12 represents a substrate. In other embodiments in which a bulksemiconductor substrate is used, a remaining portion of the bulksubstrate serves as a substrate in which the plurality of semiconductorfins extend from. The plurality of semiconductor fins (14L, 14R) can beformed by patterning the semiconductor material layer 14 of the SOIsubstrate shown in FIGS. 1A-1B. Alternatively, and when a bulksemiconductor substrate is employed as the exemplary semiconductorstructure of FIGS. 1A-1B, a topmost semiconductor material of a bulksemiconductor substrate can be subjected to a patterning process.

In the drawings, semiconductor fins labeled as 14L represent a first setof semiconductor fins that is present in a first area of the structure,while semiconductor fins 14R represent a second set of semiconductorfins that is present in a second area of the structure. The first areaof the structure containing the first set of semiconductor fins 14L iswithin a FinFET device region of the structure, while the second area ofthe structure containing the second set of semiconductor fins 14R iswithin a fill/Kerf region of the structure. The Kerf (or fill) region isan area of the structure in which active devices are not formed.

In one embodiment of the present application, the patterning processcomprises a sidewall image transfer (SIT) process. The SIT processincludes forming a contiguous mandrel material layer (not shown) on atopmost surface of either the bulk semiconductor substrate describedabove or the semiconductor material layer 14 of the SOI substratedescribed above. The contiguous mandrel material layer (not shown) caninclude any material (semiconductor, dielectric or conductive) that canbe selectively removed from the structure during a subsequentlyperformed etching process. In one embodiment, the contiguous mandrelmaterial layer (not shown) may be composed of amorphous silicon orpolysilicon. In another embodiment, the contiguous mandrel materiallayer (not shown) may be composed of a metal such as, for example, Al,W, or Cu. The contiguous mandrel material layer (not shown) can beformed, for example, by chemical vapor deposition or plasma enhancedchemical vapor deposition. The thickness of the contiguous mandrelmaterial layer (not shown) can be from 50 nm to 300 nm, although lesserand greater thicknesses can also be employed. Following deposition ofthe contiguous mandrel material layer (not shown), the contiguousmandrel material layer (not shown) can be patterned by lithography andetching to form a plurality of mandrel structures (also not shown) onthe topmost surface of the structure.

The SIT process continues by forming a dielectric spacer on eachsidewall of each mandrel structure. The dielectric spacer can be formedby deposition of a dielectric spacer material and then etching thedeposited dielectric spacer material. The dielectric spacer material maycomprise any dielectric spacer material such as, for example, silicondioxide, silicon nitride or a dielectric metal oxide. Examples ofdeposition processes that can be used in providing the dielectric spacermaterial include, for example, chemical vapor deposition (CVD), plasmaenhanced chemical vapor deposition (PECVD), or atomic layer deposition(ALD). Examples of etching that be used in providing the dielectricspacers include any etching process such as, for example, reactive ionetching.

After formation of the dielectric spacers, the SIT process continues byremoving each mandrel structure. Each mandrel structure can be removedby an etching process that is selective for removing the mandrelmaterial. Following the mandrel structure removal, the SIT processcontinues by transferring the pattern provided by the dielectric spacerspartially through an upper semiconductor material portion of the bulksemiconductor substrate, or entirely through the semiconductor materiallayer 14 of the SOI substrate and stopping on the insulator layer 12.The pattern transfer may be achieved by utilizing at least one etchingprocess. Examples of etching processes that can used to transfer thepattern may include dry etching (i.e., reactive ion etching, plasmaetching, ion beam etching or laser ablation) and/or a chemical wet etchprocess. In one example, the etch process used to transfer the patternmay include one or more reactive ion etching steps. Upon completion ofthe pattern transfer, the SIT process concludes by removing thedielectric spacers from the structure. Each dielectric spacer may beremoved by etching or a planarization process.

In another embodiment, the patterning process can include lithographyand etching. Lithography includes forming a photoresist material (notshown) on a topmost surface of either the bulk semiconductor substratedescribed above or the semiconductor material layer 14 of the SOIsubstrate described above. The photoresist material can be formedutilizing a deposition process such as, for example, spin-on coating,evaporation, or chemical vapor deposition. Following the deposition ofthe photoresist material, the photoresist material is exposed to apattern of irradiation, and thereafter the exposed resist material isdeveloped utilizing a conventional resist developer to provide apatterned photoresist material. At least one etch as mentioned above forthe SIT process can be used here to complete the pattern transfer.Following at least one pattern transfer etch process, the patternedphotoresist material can be removed from the structure utilizing aconventional resist stripping process such as, for example, ashing.

Each semiconductor fin (14L, 14R) that is formed includes a pair ofvertical sidewalls that are parallel to each other. As used herein, asurface is “vertical” if there exists a vertical plane from which thesurface does not deviate by more than three times the root mean squareroughness of the surface. In one embodiment of the present application,each semiconductor fin (14L, 14R) that is formed has a height from 10 nmto 150 nm, and a width from 5 nm to 30 nm. Other heights and widths thatare lesser than, or greater than, the aforementioned ranges may also beused in the present application for each semiconductor fin (14L, 14R).When multiple semiconductor fins are present in a given area of thestructure, each semiconductor fin (14L or 14R) is separated from itsnearest neighboring semiconductor fin (14L or 14R) by a pitch that isfrom 20 nm to 60 nm; the pitch can be measured from a central portion ofone semiconductor fin to a central portion of the nearest neighboringsemiconductor fin. Each semiconductor fin (14L, 14R) includes one of thesemiconductor materials mentioned above for the bulk semiconductorsubstrate or the semiconductor material layer 14 of the SOI substrate.

In some embodiments not shown, a local isolation structure can be formedat the footprint of each semiconductor fin at this point of the presentapplication. The local isolation structure can be formed by depositionof a trench dielectric material such as, a trench dielectric oxide, andthereafter a recess etch may be used to provide the local isolationstructure. In embodiments in which the local isolation structure ispresent, a local isolation structure is present adjacent eachsemiconductor fin.

Referring now to FIGS. 3A-3B, there are illustrated various views of theexemplary semiconductor structure of FIGS. 2A-2B after forming aprotective dielectric liner 18 on exposed surfaces of each semiconductorfin (14L, 14R) and on exposed portions of the insulator layer 12; when abulk semiconductor substrate is used, a portion of the protectivedielectric liner 18 would be located on a remaining portion of the bulksemiconductor substrate. In some embodiments of the present application,the formation of the protective dielectric liner 18 can be omitted.

The protective dielectric liner 18 can be composed of an oxide, nitrideand/or oxynitride. In one example, silicon dioxide is used for providingthe protective dielectric liner 18. In some embodiments of the presentapplication, the protective dielectric liner 18 can be formed by adeposition process including, for example, chemical vapor deposition,plasma enhanced chemical vapor deposition or physical vapor deposition.In other embodiments of the present application, the protectivedielectric liner 18 can be formed by a thermal growth process such as,for example, oxidation.

The protective dielectric liner 18 is a conformal layer meaning that ithas a thickness that is substantially the same (within ±0.5 nm)everywhere along an interface with each semiconductor fin (14L, 14R) andthe surface of insulator layer 12. In one embodiment, the thickness ofthe protective dielectric liner 18 is from 10 nm to 50 nm. Otherthicknesses are possible and are not excluded from being used in thepresent application.

Referring now to FIGS. 4A-4B, there are illustrated various views of theexemplary semiconductor structure of FIGS. 3A-3B after forming asacrificial dielectric material 20. As is shown, the sacrificialdielectric material 20 fills the gaps located between each semiconductorfin (14L, 14R) and a portion of the sacrificial dielectric material 20extends above a portion of the protective dielectric liner 18 that ispresent on a topmost surface of each semiconductor fin (14L, 14R).

The sacrificial dielectric material 20 may include one of the dielectricmaterials mentioned above for the protective dielectric liner 18. In oneembodiment of the present application, the sacrificial dielectricmaterial 20 and the protective dielectric liner 18 comprise a samesemiconductor material. For example, the sacrificial dielectric material20 and the protective dielectric liner 18 may both be comprised ofsilicon dioxide. In another embodiment of the present application, thesacrificial dielectric material 20 comprises a different dielectricmaterial than the protective dielectric liner 18. For example, thesacrificial dielectric material 20 may comprise silicon dioxide, whilethe protective dielectric liner 18 comprises silicon oxynitride.

The sacrificial dielectric material 20 may be formed utilizing adeposition process including, for example, chemical vapor deposition orplasma enhanced chemical vapor deposition. The thickness of thesacrificial dielectric material 20 can be from 50 nm to 200 nm. Otherthicknesses that are lesser than, or greater than, the aforementionedthickness range may also be employed as the thickness of the sacrificialdielectric material 20.

Referring now to FIGS. 5A-5B, there are illustrated various views of theexemplary semiconductor structure of FIGS. 4A-4B after removing an upperportion of the sacrificial dielectric material 20 and a portion (i.e.,topmost horizontal portion) of the protective dielectric liner 18 toexpose a topmost surface of each semiconductor fin (14L, 14R). Eachremaining portion of the sacrificial dielectric material 20 may bereferred herein as sacrificial dielectric material portion 20P, and eachremaining portion of the protective dielectric liner 18 may be referredherein as protective dielectric liner portion 18P.

In one embodiment, the removal of the upper portion of the sacrificialdielectric material 20 and the topmost horizontal portion of theprotective dielectric liner 18 may include a planarization process such,as for example, chemical mechanical polishing or grinding. In anotherembodiment, the removal of the upper portion of the sacrificialdielectric material 20 and the topmost horizontal portion of theprotective dielectric liner 18 may include one or more etch backprocesses. In yet a further embodiment of the present application, aplanarization process, followed by an etch back process can be used toremove the upper portion of the sacrificial dielectric material 20 andthe topmost horizontal portion of the protective dielectric liner 18.

As is shown in FIGS. 5A-5B, the topmost surface of each semiconductorfin (14L, 14R) is now exposed. As is further shown, the topmost surfaceof each semiconductor fin (14L, 14R) is coplanar with a topmost surfaceof each sacrificial dielectric material portion 20P and a topmostsurface of each protective dielectric liner portion 18P. As is furthershown, each protective dielectric liner portion 18P is U-shaped. By“U-shaped” it is meant a structure having a base in which a verticalportion extends upward from each end portion of the base. Eachsacrificial dielectric portion 20P is located within the volume of aU-shaped protective dielectric liner portion 18P.

Referring now to FIGS. 6A-6B, there are illustrated various views of theexemplary semiconductor structure of FIGS. 5A-5B after forming a blockmask structure 22 over the first set of the semiconductor fins 14L,while leaving the second set of semiconductor fins 14R exposed.

In one embodiment of the present application, the block mask structure22 may be composed of only a photoresist material. In anotherembodiment, the block mask structure 22 may be composed of only a hardmask material. Examples of hard mask materials that can be used as blockmask structure 22 include silicon dioxide, silicon nitride and/orsilicon oxynitride. In another embodiment of the present application,the block mask structure 22 may comprise a stack of, from bottom to top,a hard mask material and a photoresist material.

In regard to the block mask structures disclosed in the proceedingparagraph, such block mask structures can be formed utilizing techniquesthat are well known to those skilled in the art. For example, the blockmask structure 22 can be formed by first depositing at least one of theabove mentioned materials and then patterning the at least one depositedmaterial by lithography. An anisotropic etching process such as, forexample, reactive ion etching can also be used to complete any patterntransfer that may be needed; for example, an anisotropic etch may beused to transfer a pattern from a lithographically defined photoresistinto the underlying material that may define the block mask structure22.

In yet other embodiments of the present application, the block maskstructure 22 may include, a trilayer structure including from bottom totop, an optical planarization layer (OPL) portion, an antireflectivecoating (ARC) portion, and a photoresist material portion (all notindividually shown). In such an embodiment, the OPL portion may comprisea self-planarizing material. In one example, the OPL portion can be anorganic material including C, O, and H, and optionally including Siand/or F. In another example, the OPL portion can be amorphous carbon.The self-planarizating material that can provide the OPL portion can beformed by spin-on coating, chemical vapor deposition, plasma enhancedchemical vapor deposition, evaporation or chemical solution deposition.The thickness of the OPL portion can be from 10 nm to 300 nm, althoughlesser and greater thicknesses can also be employed.

The ARC portion comprises any antireflective coating material that canreduce image distortions associated with reflections off the surface ofunderlying structure. In one example, the ARC portion comprises asilicon (Si)-containing antireflective coating material. Theantireflective coating material that provides the ARC portion can beformed by spin-on coating, chemical vapor deposition, plasma enhancedchemical vapor deposition, evaporation or chemical solution deposition.The thickness of the ARC portion can be from 10 nm to 150 nm, althoughlesser and greater thicknesses can also be employed.

When employed as the block mask structure 22, the trilayer structuredescribed above can be formed by first providing a material stack of,from bottom to top, a blanket layer of self-planarizing material (asdefined above), a blanket layer of antireflective coating material (asdefined above) and a blanket layer of a photoresist material. Theblanket layer of self-planarizing material and the blanket layer ofantireflective coating material can be formed utilizing one of thedeposition processes mentioned above. The photoresist material that mayprovide the blanket layer of photoresist material may comprise apositive-tone photoresist, a negative tone-resist or a hybridphotoresist material. The blanket layer of photoresist material may bedeposited utilizing one of the deposition processes mentioned above inproviding the antireflective coating material. After providing such amaterial stack, the material stack is then patterned by lithography andetching both of which have been described above.

Referring now to FIGS. 7A-7B, there are illustrated various views of theexemplary semiconductor structure of FIGS. 6A-6B after removing eachsemiconductor fin of the second set of semiconductor fins 14R. Theremoval of each semiconductor fin of the second set of semiconductorfins 14R can be performed utilizing an anisotropic etching process thatis selective in removing the semiconductor material that provides eachsemiconductor fin of the second set of semiconductor fins 14R. In oneexample, a reactive ion etch can be used to remove each semiconductorfin of the second set of semiconductor fins 14R. The removal of eachsemiconductor fin of the second set of semiconductor fins 14R exposesportions of the insulator layer 12 within the fill/Kerf area of thestructure.

Referring now to FIGS. 8A-8B, there are illustrated various views of theexemplary semiconductor structure of FIGS. 7A-7B after removing theblock mask structure 22 and forming a sacrificial spacer material 24.The removal of the block mask structure 22 may include any materialremoval process that is well known to those skilled in the art. Thisincludes, but is not limited to, photoresist stripping, planarization,and/or etching.

After removing the block mask structure 22, the sacrificial spacermaterial 24 is formed. The sacrificial spacer material 24 comprises adielectric material that has a different etch rate in a selectiveetchant as compared to both the protective dielectric liner 18 and thesacrificial dielectric material 20. In one embodiment of the presentapplication, the sacrificial spacer material 24 comprises siliconnitride, while the protective dielectric liner 18 and the sacrificialdielectric material 20 comprise silicon dioxide. The sacrificial spacermaterial 24 can be formed utilizing any deposition process including,for example, chemical vapor deposition or plasma enhanced chemical vapordeposition. The thickness of the sacrificial spacer material 24 can befrom 50 nm to 200 nm. Other thicknesses that are lesser than, or greaterthan, the aforementioned thickness range may also be employed as thethickness of the sacrificial spacer material 24.

As is shown, a portion of the sacrificial spacer material 24 extendsabove each semiconductor fin of the first set of semiconductor fins 14Lthat are in the FinFET device region. Within the fill/Kerf region, thesacrificial spacer material 24 fills in the volume that was previouslyoccupied by the set second of semiconductor fins 14R. Also, and in thefill/Kerf region, the sacrificial spacer material 24 extends atop eachsacrificial dielectric material portion 20P and each protectivedielectric liner portion 18P.

Referring now to FIGS. 9A-9B, there are illustrated various views of theexemplary semiconductor structure of FIGS. 8A-8B after removing an upperportion of the sacrificial spacer material 24 to provide sacrificialspacer fins 24P within the area previously occupied by the second set ofsemiconductor fins 14R.

In one embodiment, the removal of the upper portion of the sacrificialspacer material 24 may include a planarization process such, as forexample, chemical mechanical polishing or grinding. In anotherembodiment, the removal of the upper portion of sacrificial spacermaterial 24 may include an etch back process.

As is shown in FIGS. 9A-9B, the topmost surface of each sacrificialspacer fin 24P is exposed. As is further shown, the topmost surface ofeach sacrificial spacer fin 24P is coplanar with a topmost surface ofeach semiconductor fin of the first set of semiconductor fins 14L, eachsacrificial dielectric material portion 20P and a topmost surface ofeach protective dielectric liner portion 18P.

Referring now to FIGS. 10A-10B, there are illustrated various views ofthe exemplary semiconductor structure of FIGS. 9A-9B after removingremaining portions of the sacrificial dielectric material (i.e.,sacrificial dielectric material portions 20P) and remaining portions ofthe protective dielectric liner (i.e., protective dielectric linerportions 18P). The removal of each sacrificial dielectric materialportion 20P and each protective dielectric liner portion 18P can beperformed utilizing one or more etching processes that is (are)selective in removing the dielectric material that provides thesacrificial dielectric material portions 20P and the protectivedielectric liner portions 18P.

Upon removal of each sacrificial dielectric material portion 20P andeach protective dielectric liner portion 18P, there is provided astructure that includes a plurality of semiconductor fins (representedby the first set of semiconductor fins 14L) extending upwards from asurface of insulator layer 12, and a plurality of sacrificial spacerfins 24P extending upwards from another surface of the insulator layer12. Each semiconductor fin (i.e., the first set of semiconductor fins14L) is present in the FinFET device region, while each sacrificialspacer fin 24P is present in the fill/Kerf region. Each semiconductorfin (i.e., the first set of semiconductor fins 14L) has a height andwidth that is the same as each sacrificial spacer fin 24P.

Referring now to FIGS. 11A-11B, there are shown various views of theexemplary semiconductor structure of FIGS. 10A-10B after forming anotherprotective dielectric liner 26 on exposed surfaces of each semiconductorfin of the first set of semiconductor fins 14L, exposed surfaces of eachsacrificial spacer fin 24P and on exposed portions of the insulatorlayer 12. In some embodiments of the present application, the formationof the another protective dielectric liner 26 may be omitted. Theprotective dielectric liner 18 mentioned above may represent a firstprotective dielectric liner, while the another protective dielectricliner 26 may represent a second protective dielectric liner.

Protective dielectric liner 26 may include one of the materials asmentioned above for protective dielectric liner 18. Also, protectivedielectric liner 26 may be formed utilizing a deposition process asmentioned above in forming the protective dielectric liner 18.Protective dielectric liner 26 may also have a thickness within thethickness range mentioned above for protective dielectric liner 18.

Referring now to FIGS. 12A-12B, there are illustrated various views ofthe exemplary semiconductor structure of FIGS. 11A-11B after forming asacrificial gate material 28 and a photoresist material 34. In someembodiments, and as shown, a hard mask stack including a lower hard maskmaterial layer 30 and an upper hard mask material layer 32 can bepositioned between the sacrificial gate material 28 and the photoresistmaterial 34.

The sacrificial gate material 28 can include any material including, forexample, polysilicon, amorphous silicon, an elemental metal (e.g.,tungsten, titanium, tantalum, aluminum, nickel, ruthenium, palladium andplatinum), an alloy of at least two elemental metals or multilayeredcombinations thereof. The sacrificial gate material can be formedutilizing a deposition process including, for example, chemical vapordeposition (CVD), plasma enhanced chemical vapor deposition (PECVD),physical vapor deposition (PVD), sputtering, atomic layer deposition(ALD) or other like deposition processes.

After forming the sacrificial gate material 28, and in some embodiments,the hard mask stack (30, 32) mentioned can be formed. The lower hardmask material layer 30 may comprise an oxide, nitride, or an oxynitride.In one example, the lower hard mask material layer 30 may be composed ofsilicon dioxide. The upper hard mask material layer 32 typicallycomprises a different material than the lower hard mask material layer30. In one example, and when the lower hard mask material layer 30 iscomposed of silicon dioxide, the upper hard mask material layer 32 iscomposed of silicon nitride. The hard mask stack (30, 32) can be formedutilizing deposition processes well known to those skilled in the art.

The photoresist material 34 that can be employed in the presentapplication may include any of the well known positive-tone photoresistcompositions, negative-tone photoresist compositions or hybrid-tonephotoresist compositions. The photoresist material 34 can be formed by adeposition process such as, for example, chemical vapor deposition orspin-on coating.

Referring now to FIGS. 13A-13B, there are illustrated various views ofthe exemplary semiconductor of FIGS. 12A-12B after forming sacrificialgate structures straddling over different portions of each semiconductorfin of the first set of semiconductor fns 14L and each sacrificialspacer fin 24P. Although a plurality of sacrificial gate structures isdescribed and illustrated, the present application can work when only asingle sacrificial gate structure is formed.

After sacrificial gate structure formation and as is shown, portions ofeach semiconductor fin of the first set of semiconductor fins 14L andeach sacrificial spacer fin 24P are exposed. Although not seen in thetop-view of FIG. 13A, portions of each semiconductor fin of the firstset of semiconductor fins 14L and each sacrificial spacer fin 24P arelocated directly beneath each sacrificial gate structure. In someembodiments, and as shown, the another protective dielectric liner 26can be patterned during this step of the present application. In yetanother embodiment, the another protective dielectric liner 26 remainsunpatterned after forming the sacrificial gate structure.

Each sacrificial gate structure includes, from bottom to top, aremaining portion of the sacrificial gate material 28, a remainingportion of the lower hard mask material layer 30, and a remainingportion of the upper hard mask material layer 32. In some embodiments,and as shown, the another protective dielectric liner 26 can bepatterned during this step of the present application. The remainingportion of the another protective dielectric liner 26 can be referred toherein as another protective dielectric liner portion 26P. In yetanother embodiment, the another protective dielectric liner 26 remainsunpatterned after forming the sacrificial gate structure.

The remaining portion of the sacrificial gate material 28 can bereferred to herein as a sacrificial gate material portion 28P. Theremaining portion of the lower hard mask material layer 30 can bereferred to herein as lower hard mask material portion 30P. Theremaining portion of the upper hard mask material layer 32 can bereferred to herein as upper hard mask material portion 32P. Within aparticular sacrificial gate structure (28P, 30P, 32P), the sidewallsurfaces of elements 28P, 30P and 32P are vertically coincident witheach other. When the another protective dielectric liner 26 ispatterned, the sidewall surfaces of the another protective dielectricliner portion 26P are vertically coincident to the sidewall surfaces ofeach of elements 28P, 30P and 32P.

Each sacrificial gate structures (28P, 30P, 32P) can be formed bylithography and etching of the exemplary semiconductor structureillustrated in FIGS. 12A-12B. The lithography step include exposing thephotoresist material to a pattern of irradiation and then developing theexposed resist utilizing a conventional resist developer to provide apatterned photoresist material (not shown) atop a portion of the hardmask stack (30, 32). One or more anisotropic etching processes can beused to transfer the pattern from the patterned photoresist materialinto the underlying hard mask stack (30, 32) and then into thesacrificial gate material 28. In some embodiments, and when theprotective dielectric liner 26 is patterned at this point of the presentapplication, the pattern transfer etch continues into the underlyingprotective dielectric liner 26. The patterned photoresist material canbe removed any time after the pattern has been transferred into at leastthe upper hard mask material layer 32 utilizing a conventional resiststripping process such as, for example, ashing.

It should be noted that the exemplary semiconductor structure shown inFIG. 13B represents one possible configuration. In the illustratedexemplary semiconductor structure of FIG. 13B, the outermost sacrificialgate structures (28P, 30P, 32P) are shown at the outermost edge of thesemiconductor fin 14L. In other embodiments of the present application,the outermost sacrificial gate structures (28P, 30P, 32P) can be locatedinward from the outermost edge of the semiconductor fin 14L. In yetanother embodiment, a portion of each outermost sacrificial gatestructures (28P, 30P, 32P) can extend beyond the outermost edge of thesemiconductor fin 14L and can be positioned on a surface of a previouslyformed local isolation structure.

Referring now to FIGS. 14A-14B, there are illustrated various views ofthe exemplary semiconductor structure of FIGS. 13A-13B after forming adielectric spacer material 36. Dielectric spacer material 36 comprises adielectric material that is the same as the dielectric material thanprovides each sacrificial spacer fin 24P. In one example, the dielectricspacer material 36 and each sacrificial spacer fin 24P comprise siliconnitride.

The dielectric spacer material 36 can be formed by a deposition processincluding, for example, chemical vapor deposition, plasma enhancedchemical vapor deposition or physical vapor deposition. The dielectricspacer material 36 is a conformal layer whose thickness can be from 5 nmto 30 nm. Other thicknesses are possible and are not excluded from beingused in the present application.

Referring now to FIGS. 15A-15D, there are illustrated various views ofthe exemplary semiconductor structure of FIGS. 14A-14B after performinga spacer reactive ion (RIE) etch. The spacer RIE forms a dielectricspacer 36P that surrounds each sacrificial gate structure (28P, 30P,32P); dielectric spacer 36P may also be referred to as a gate spacer.Also, and during the spacer RIE, the exposed portions of eachsacrificial spacer fin 24P are removed. Portions of each sacrificialspacer fin 24P remain under each sacrificial gate structure (28P, 30P,32P) as well as a portion of the newly formed dielectric spacer 36P.Each remaining portion of sacrificial spacer fin can be referred toherein as a sacrificial spacer fin portion 25. In FIG. 15A, theremaining portions of each sacrificial spacer fin 24P are shown forillustrative purposes only; in reality one would not see the remainingportions of each sacrificial spacer fin 24P (i.e., sacrificial spacerfin portions 25) that is present beneath the sacrificial gate structures(28P, 30P, 32P). Although not shown in the top down view of FIG. 15A, aportion of each semiconductor fin 14L that is present in a first area ofthe structure is located beneath the sacrificial gate structure (28P,30P, 32P) and well as the dielectric spacer 26P. In the presentapplication, each semiconductor fin of the first set of semiconductorfins 14L has a height and width that is the same as each sacrificialspacer fin portion 25.

It is noted that the presence of the sacrificial spacer fin 24P in theexemplary semiconductor structure of the present application increasesthe endpoint signal intensity of the RIE process thus providing anenhanced (i.e., greater signal intensity) endpoint signal that can bereliably detected over the same structure that does not include thesacrificial spacer fins 24P. Thus, the presence of the sacrificialspacer fin 24P in the exemplary semiconductor structure of the presentapplication improves the accuracy of the spacer RIE such that there issufficient space in the FinFET device region for subsequently formingsource/drain structures by epitaxial growth of a semiconductor material.

Although not illustrated in the drawings, source/drain structures can beformed after performing the spacer RIE mentioned above. The source/drainstructures (not shown) would be epitaxially grown on the exposedsurfaces of each semiconductor fin of the first set of semiconductorfins 14L that are not covered by the dielectric spacer 36P and thesacrificial gate structure. If not previously done, the anotherprotective dielectric liner 26 can be removed from the semiconductorfins 14L at this point of the present application by etching. As isknown to those skilled in the art, a source structure would be locatedon one side of the sacrificial gate structure, while a drain structurewould be located on another side of the sacrificial gate structure. Thesource/drain structures of each individual semiconductor fin 14L may beunmerged or merged. The source/drain structures typically have a heightthat is greater than a height of the semiconductor fins 14L.

The terms “epitaxial growth and/or deposition” and “epitaxially formedand/or grown” mean the growth of a semiconductor material on adeposition surface of a semiconductor material, in which thesemiconductor material being grown has the same crystallinecharacteristics as the semiconductor material of the deposition surface.In an epitaxial deposition process, the chemical reactants provided bythe source gases are controlled and the system parameters are set sothat the depositing atoms arrive at the deposition surface of asemiconductor material with sufficient energy to move around on thesurface and orient themselves to the crystal arrangement of the atoms ofthe deposition surface. Therefore, an epitaxial semiconductor materialthat is formed by an epitaxial deposition process has the samecrystalline characteristics as the deposition surface on which it isformed. For example, an epitaxial semiconductor material deposited on a{100} crystal surface will take on a {100} orientation. In the presentapplication, each source/drain structure has an epitaxial relationship,i.e., same crystal orientation, as that of the semiconductor fins 14L.

Examples of various epitaxial growth processes that are suitable for usein forming the source/drain structures include, e.g., rapid thermalchemical vapor deposition (RTCVD), low-energy plasma deposition (LEPD),ultra-high vacuum chemical vapor deposition (UHVCVD), atmosphericpressure chemical vapor deposition (APCVD), molecular beam epitaxy (MBE)or metal-organic CVD (MOCVD). The temperature for epitaxial depositiontypically ranges from 250° C. to 900° C. Although higher temperaturetypically results in faster deposition, the faster deposition may resultin crystal defects and film cracking. A number of different source gasesmay be used for the deposition of the source/drain structures. In someembodiments, the source gas for the deposition of a silicon source/drainstructure includes a silicon containing gas source such as, for example,a silane. When a silicon germanium alloy is used as the semiconductormaterial of the source/drain structures, a silicon containing gas sourceand a separate germanium containing gas source may be used. Carriergases like hydrogen, nitrogen, helium and argon can be used.

The semiconductor material that provides the source/drain structures isdoped with an n-type dopant or a p-type dopant as are well known thoseskilled in the art. The doping may be achieved during the epitaxialgrowth of the semiconductor material that provides the source/drainstructures or after epitaxial growth of an intrinsic semiconductormaterial by utilizing ion implantation or gas phase doping.

The term “p-type” refers to the addition of impurities to an intrinsicsemiconductor that creates deficiencies of valence electrons. In asilicon-containing substrate, examples of p-type dopants, i.e.,impurities, include, but are not limited to, boron, aluminum, galliumand indium. “N-type” refers to the addition of impurities thatcontributes free electrons to an intrinsic semiconductor. In a siliconcontaining substrate, examples of n-type dopants, i.e., impurities,include, but are not limited to, antimony, arsenic and phosphorous. Theconcentration of dopants within semiconductor material that provides thesource/drain structures can be within ranges typically used in formingmetal oxide semiconductor field effect transistors (MOSFETs).

Referring now to FIGS. 16A-16B, there is illustrated various views ofthe exemplary semiconductor structure of FIGS. 15A-15D after replacingeach sacrificial gate structure (28P, 30P, 32P) with a functional gatestructure (40, 42). In some embodiments, the another protectivedielectric liner portion 26P that is located beneath each sacrificialgate structure (28P, 30P, 32P) can be removed at this point of thepresent application utilizing an etching step. Each functional gatestructure (40, 42) straddles over each semiconductor fin 14L. Althoughnot shown in FIG. 16A, the sacrificial spacer fins portions 25 remain inthe structure and, in some embodiments, are present beneath a portion ofthe functional gate structure (40, 42).

The exemplary semiconductor structure shown in FIGS. 16A-16B representsone possible configuration. It is also possible to cut the sacrificialgate structures prior to forming the functional gate structures suchthat each functional gate structure is only present in the FinFET deviceregion. In another embodiment, the functional gate structures shown inFIGS. 16A-16B can be cut after their formation such that the functionalgate structures only remain in the FinFET device region.

The replacing of each sacrificial gate structure (28P, 30P, 32P)includes first forming an interlevel dielectric (ILD) material 38 havinga topmost surface that is coplanar with a topmost surface of thedielectric spacer 36P and a topmost surface of each sacrificial gatestructure (28P, 30P, 32P). In some embodiments, the ILD material 38 maybe composed of, for example, silicon dioxide, undoped silicate glass(USG), fluorosilicate glass (FSG), borophosphosilicate glass (BPSG), aspin-on low-k dielectric layer, a chemical vapor deposition (CVD) low-kdielectric layer or any combination thereof. The term “low-k” as usedthroughout the present application denotes a dielectric material thathas a dielectric constant of less than silicon dioxide. In anotherembodiment, a self-planarizing material such as a spin-on glass (SOG) ora spin-on low-k dielectric material such as SiLK™ can be used as the ILDmaterial 38. The use of a self-planarizing dielectric material as ILDmaterial 38 may avoid the need to perform a subsequent planarizing step.In one embodiment, the ILD material 38 can be formed utilizing adeposition process including, for example, chemical vapor deposition(CVD), plasma enhanced chemical vapor deposition (PECVD), evaporation orspin-on coating. In some embodiments, particularly whennon-self-planarizing dielectric materials are used as the ILD material38, a planarization process or an etch back process follows thedeposition of the ILD material 38. The thickness of the ILD material 38that can be employed in the present application may vary depending onthe type of dielectric material employed as well as the method that wasemployed in forming the same. In one embodiment, the ILD material 38 hasa thickness from 80 nm to 500 nm. Other thicknesses that are greater orlesser than the range provided above can also be used for the ILDmaterial 38.

After forming the ILD material 38, each sacrificial gate structure (28P,30P, 32P) is removed providing a gate cavity (not shown). The eachsacrificial gate structure (28P, 30P, 32P) may be removed utilizing anetch process (or etching processes) that is (are) selective in removingthe materials that provide each sacrificial gate structure (28P, 30P,32P). Next, a functional gate structure (40, 42) is formed in each gatecavity and each functional gate structure (40, 42) straddles over aportion of each semiconductor fin 14L. The term “straddling” denotesthat each functional gate structure (40, 42) spans over eachsemiconductor fin 14L. Portions of each first functional gate structure(40, 42) contact sidewall surfaces and, in some instances, a topmostsurface of each semiconductor fin 14L.

By “functional gate structure” it is meant a permanent gate structureused to control output current (i.e., flow of carriers in the channel)of a semiconducting device through electrical or magnetic fields. Eachfunctional gate structure that is formed includes a gate material stackof, from bottom to top, a gate dielectric portion 40 and a gateconductor portion 42. In some embodiments, a gate cap portion (notshown) can be present atop the gate conductor portion 42.

The gate dielectric portion 40 comprises a gate dielectric material. Thegate dielectric material that provides the gate dielectric portion 40can be an oxide, nitride, and/or oxynitride. In one example, the gatedielectric material that provides the gate dielectric portion 40 can bea high-k material having a dielectric constant greater than silicondioxide. Exemplary high-k dielectrics include, but are not limited to,HfO₂, ZrO₂, La₂O₃, Al₂O₃, TiO₂, SrTiO₃, LaAlO₃, Y₂O₃, HfO_(x)N_(y),ZrO_(x)N_(y), La₂O_(x)N_(y), Al₂O_(x)N_(y), TiO_(x)N_(y),SrTiO_(x)N_(y), LaAlO_(x)N_(y), Y₂O_(x)N_(y), SiON, SiN_(x), a silicatethereof, and an alloy thereof. Each value of x is independently from 0.5to 3 and each value of y is independently from 0 to 2. In someembodiments, a multilayered gate dielectric structure comprisingdifferent gate dielectric materials, e.g., silicon dioxide, and a high-kgate dielectric can be formed and used as the gate dielectric portion40.

The gate dielectric material used in providing the gate dielectricportion 40 can be formed by any deposition process including, forexample, chemical vapor deposition (CVD), plasma enhanced chemical vapordeposition (PECVD), physical vapor deposition (PVD), sputtering, oratomic layer deposition. In some embodiments, the gate dielectricportion 40 of each functional gate structure comprises a same gatedielectric material. In other embodiments, the gate dielectric portionof some of the functional gate structure may comprise a different gatedielectric material than the gate dielectric portion of other functionalgate structures. When a different gate dielectric material is used forthe gate dielectric portions, block mask technology can be used. In oneembodiment of the present application, the gate dielectric material usedin providing the gate dielectric portion 40 can have a thickness in arange from 1 nm to 10 nm. Other thicknesses that are lesser than, orgreater than, the aforementioned thickness range can also be employedfor the gate dielectric material.

The gate conductor portion 42 comprises a gate conductor material. Thegate conductor material used in providing the gate conductor portion 42can include any conductive material including, for example, dopedpolysilicon, an elemental metal (e.g., tungsten, titanium, tantalum,aluminum, nickel, ruthenium, palladium and platinum), an alloy of atleast two elemental metals, an elemental metal nitride (e.g., tungstennitride, aluminum nitride, and titanium nitride), an elemental metalsilicide (e.g., tungsten silicide, nickel silicide, and titaniumsilicide) or multilayered combinations thereof. In some embodiments, thegate conductor portion of each functional gate structure may comprise asame gate conductor material. In other embodiments, the gate conductorportion of some of the functional gate structures comprises a differentgate conductor material from gate conductor portion of other functionalgate structures. In some embodiments, gate conductor portion 42 maycomprise an nFET gate metal or a p-FET gate metal.

The gate conductor material used in providing the gate conductor portion42 can be formed utilizing a deposition process including, for example,chemical vapor deposition (CVD), plasma enhanced chemical vapordeposition (PECVD), physical vapor deposition (PVD), sputtering, atomiclayer deposition (ALD) or other like deposition processes. When a metalsilicide is formed, a conventional silicidation process is employed.When a different gate conductor material is used for the gate conductorportions, block mask technology can be used. In one embodiment, the gateconductor material used in providing the gate conductor portion 42 has athickness from 1 nm to 100 nm. Other thicknesses that are lesser than,or greater than, the aforementioned thickness range can also be employedfor the gate conductor material used in providing the gate conductorportion 42.

If present, the gate cap portion comprises a gate cap material. The gatecap material that provides each gate cap portion may include one of thedielectric materials mentioned above for hard mask material. In oneembodiment, each gate cap portion comprises silicon dioxide, siliconnitride, and/or silicon oxynitride. The dielectric material thatprovides each gate cap portion can be formed utilizing a conventionaldeposition process such as, for example, chemical vapor deposition orplasma enhanced chemical vapor deposition. The dielectric material thatprovides each gate cap portion can have a thickness from 5 nm to 20 nm.Other thicknesses that are lesser than, or greater than, theaforementioned thickness range can also be employed as the thickness ofthe dielectric material that provides each gate cap portion.

Each functional gate structure (40, 42) can be formed by providing afunctional gate material stack of, from bottom to top, the gatedielectric material, the gate conductor material and, if present, thegate cap material. The functional gate material stack can then bepatterned. In one embodiment of the present application, patterning ofthe functional gate material stack may be performed utilizinglithography and etching.

While the present application has been particularly shown and describedwith respect to preferred embodiments thereof, it will be understood bythose skilled in the art that the foregoing and other changes in formsand details may be made without departing from the spirit and scope ofthe present application. It is therefore intended that the presentapplication not be limited to the exact forms and details described andillustrated, but fall within the scope of the appended claims.

What is claimed is:
 1. A semiconductor structure comprising: a pluralityof semiconductor fins extending upwards from a first portion of asubstrate; a plurality of sacrificial spacer fin portions extendingupwards from a second portion of said substrate; a gate structurestraddling over each semiconductor fin and each sacrificial spacer finportion; a gate spacer surrounding said gate structure, wherein anentirety of each sacrificial spacer fin portion is located beneath aportion of said gate structure and a portion of said gate spacer,wherein said gate structure is a functional gate structure comprising aU-shaped gate dielectric portion that has a topmost surface that iscoplanar with a topmost surface of said gate spacer.
 2. Thesemiconductor structure of claim 1, wherein said substrate is aninsulator layer.
 3. The semiconductor structure of claim 1, wherein saidgate spacer and each sacrificial spacer fin portion comprise a samedielectric material.
 4. The semiconductor structure of claim 3, whereinsaid same dielectric material is silicon nitride.
 5. The semiconductorstructure of claim 1, wherein said semiconductor fins are present in aFinFET device region, while each sacrificial spacer fin portion ispresent in a kerf region.
 6. The semiconductor structure of claim 1,wherein each of the plurality of semiconductor fins has a height andwidth that is the same as each sacrificial spacer fin portion.
 7. Thesemiconductor structure of claim 6, wherein each sacrificial spacer finportion has a same pitch as a pitch of each semiconductor fin.
 8. Thesemiconductor structure of claim 1, wherein a first portion of eachsemiconductor fin is located beneath said gate structure and a portionof said gate spacer, and a second portion of each semiconductor fin,which is contiguous with the first portion, extends beyond the outermostedge of the gate spacer.
 9. The semiconductor structure of claim 8,further comprising a source/drain region located on the second portionof each semiconductor fin and on both sides of said gate structure. 10.The semiconductor structure of claim 1, further comprising an interleveldielectric material contacting physically exposed sidewalls of said gatespacer and having a bottommost surface located directly on a physicallyexposed surface of said substrate.
 11. The semiconductor structure ofclaim 10, wherein said interlevel dielectric material has a topmostsurface that is coplanar with a topmost surface of said gate spacer. 12.The semiconductor structure of claim 1, wherein said semiconductor finsand said sacrificial spacer fin portions are spaced apart from eachother, and are oriented parallel to each other.
 13. The semiconductorstructure of claim 1, wherein each semiconductor fin has a bottommostsurface that is located on said substrate, and is coplanar with abottommost surface of each sacrificial spacer fin portion.
 14. Asemiconductor structure comprising: a plurality of semiconductor finsextending upwards from a first portion of a substrate; a plurality ofsacrificial spacer fin portions extending upwards from a second portionof said substrate; a gate structure straddling over each semiconductorfin and each sacrificial spacer fin portion; and a gate spacersurrounding said gate structure, wherein an entirety of each sacrificialspacer fin portion is located beneath a portion of said gate structureand a portion of said gate spacer, wherein said gate structure is asacrificial gate structure, and wherein a portion of a protectivedielectric liner is positioned between a bottommost surface of saidsacrificial gate structure and a topmost surface of said semiconductorfins, and said portion of said protective dielectric liner has sidewallsurfaces that are vertically coincident to sidewall surfaces of saidsacrificial gate structure.